Dissertations / Theses on the topic 'Renewable materials'

Renewable resources related to biomass, waste materials and recycled materials are an important concept in the principles of green chemistry, development of biorefineries and sustainability development. This thesis reports the repurposing of renewable resources which included wheat straw, biomass ash, waste cardboard (paper) and paper de-inking residues (DIR) to extract, synthesize and produce potentially high value chemicals, materials and composites. Biosilicate solutions were successfully extracted from biomass ash including wheat straw ash and miscanthus ash with aqueous potassium hydroxide solutions. Systematic analyses had been applied on the extraction of biosilicate solutions to obtain different types of silicate solutions for further applications of binder and mesoporous materials. Biosilicate solutions extracted from miscanthus ash were utilized as binders to make bioboards, whilst biosilicate solutions extracted from wheat straw ash were utilized as a silica resource to synthesize biobased mesoporous materials, namely bio-MCM-41 and bio-SBA-15. N2 porosimetry analysis revealed that mesoporous silica made from biosilicate solutions gave a surface area of bio-MCM-41 of >1000 m2 g-1 and a surface area of >800 m2 g-1 for bio-SBA-15. XRD, SEM and TEM analyses for both bio-MCM-41 and bio-SBA-15 revealed significant ordering pores, structure and the hexagonal arrays. Different kinds of renewable resources including wheat straw, pea pod waste and paper de-inking residue with the binder of biosilicate solutions and other chemical additives such as protein and starch were processed to bioboards. Also, wheat straw powder was added into cardboard/paper sheets to decrease the cost of paper manufacture and to improve mechanical properties. De-waxed wheat straw cardboard/paper sheets was successfully incorporated in to paper pulp to give a tensile index of 30-34 Nm/g similar with respect to conventional cardboard paper (tensile index of 30-32 Nm/g). A brief study to elicit sugars to the surface of cardboard/paper thus producing an in-situ sticky surface using low temperature microwave irradiation was conducted. Although it’s not conclusive, an aqueous fraction was expelled that contains organic matter (based on C-H stretch absorption bands noted in FT-IR), which may be due to sugars.

La síntesis de polímeros a partir de fuentes renovables como la biomasa es una forma viable de resolver los problemas relacionados con la contaminación del medio ambiente y la escasez de recursos derivados del petróleo usados como materias primas en la industria de los polímeros. Las polibenzoxazinas son una nueva clase de resinas termoestables cuya síntesis es de gran simplicidad y presentan propiedades interesantes de potencial aplicación en diversos campos, entre otros en la industria electrónica. Además, las benzoxazinas eliminan el problema de la liberación de subproductos de condensación, que presentan las resinas fenólicas convencionales, y no necesitan de un catalizador para su entrecruzamiento. También ofrecen una mayor flexibilidad en el diseño estructural al poder utilizar fenoles y aminas de diferente estructura. Tradicionalmente, las benzoxazinas se sintetizan a partir de fuentes derivadas del petróleo como fenoles, aldehídos y aminas primarias. Son escasos los ejemplos de síntesis de benzoxazinas parcial o totalmente derivadas de fuentes renovables. Dentro de ellas, cabe destacar el uso del cardanol, compuesto extraído del aceite de la cáscara del anacardo, y más recientemente el uso de gliceroles parcialmente enriquecidos, provenientes del aceite de girasol, en la síntesis de polibenzoxazinas con buenas propiedades de flexibilidad y adherencia. A partir de procesos de biorefineria de la celulosa se obtiene el ácido levulínico. Este compuesto es de gran interés a nivel industrial debido a que su producción es simple y se obtiene con altos rendimientos. Una de sus aplicaciones es como precursor en la producción industrial del ácido difenólico, que se obtiene mediante una reacción de condensación de éste con fenol. En los últimos años la Organización Mundial de la Salud ha prestado especial atención a aquellas sustancias de uso diario que representan una amenaza para la salud humana. Entre ellas están los ftalatos, las benzofenonas, los parabenos y el bisfenol A (BPA). Actualmente el ácido difenólico se está considerando como una alternativa “green” para sustituir al BPA ya que presenta una estructura química muy similar, es más barato y además posee una funcionalidad extra, que le brinda cierta versatilidad en la síntesis de polímeros. De acuerdo a todo lo mencionado anteriormente la presente tesis aborda la utilización del ácido difenólico como material de partida para la síntesis de nuevas polibenzoxazinas con un alto valor añadido. De esta forma, diferentes estrategias se han desarrollado para explorar las diferentes aplicaciones de estos materiales que se han agrupado en distintos capítulos, que a continuación se mencionan. En la primera parte del capítulo 1 se describe la síntesis y polimerización de dos nuevas polibenzoxazinas: la derivada del ácido difenólico (DPA-Bz) y la derivada del éster del ácido difenólico (MDP-Bz). Además, se describe la caracterización térmica y termomecánica de ambos materiales y se comparan con las de la benzoxazina derivada del bisfenol A (BPA-Bz). Como resultado de las reacciones de esterificación o transesterificación entre los grupos hidroxilos, derivados de la apertura del anillo de oxazina, y los grupos carbonilo y éster, presentes en la estructura de las benzoxazinas, la MDP-Bz y la DPA-Bz presentaron una mayor densidad de entrecruzamiento y por ende una mayor temperatura de transición vítrea (Tg) en comparación con la BPA-Bz. En la segunda parte del capítulo se describe la preparación de mezclas entre el DPA y la MDP-Bz reforzadas con fibra de vidrio. La adición de DPA disminuyó la temperatura de polimerización de las mezclas, la Tg y las propiedades termomecánicas debido a su incorporación en la red de entrecruzamiento. Así mismo, se prepararon polibenzoxazinas retardantes a la llama mediante la adición de una sal de fosfaceno derivada del DPA. Los materiales resultantes exhibieron una buena estabilidad térmica. La primera parte del segundo capítulo trata sobre la preparación y caracterización de espumas rígidas de polibenzoxazina de baja densidad, a partir de la DPA-Bz. A través de un proceso de autoespumado en el cual se genera el agente de espumado (CO2) in situ, debido a una reacción de descarboxilación, se prepararon una serie de espumas controlando la temperatura de espumado. Los materiales resultantes se caracterizaron en función de su morfología, y propiedades térmicas y mecánicas. Un segundo estudio contempló la preparación y caracterización de espumas rígidas de polibenzoxazina retardantes a la llama. Se emplearon 2 compuestos organofosforados y se determinó la incidencia de su adición usando técnicas analíticas. Las espumas demostraron buenas propiedades retardantes y buena estabilidad térmica en comparación con las espumas sin aditivo. Finalmente, usando herramientas analíticas se propusieron modelos matemáticos para ajustar la densidad y las propiedades mecánicas (resistencia y el módulo de compresión) de las espumas retardantes a la llama en términos de las variables de espumado, es decir, la temperatura y el tiempo. En el tercer capítulo se describe la preparación de nanocompuestos poliméricos. Como matrices poliméricas se usaron la MDP-Bz, la BPA-Bz mientras que como nanoaditivos se emplearon nanotubos de carbono de pared múltiple (MWNT) entre 0.1 y 1.0 % en peso. Con el fin de conseguir un método de dispersión que fuera más respetuoso con el medio ambiente no se empleó ningún disolvente. La dispersión de los nanoaditivos en ambos monómeros se evaluó mediante medidas reológicas mientras que la dispersión en los polímeros se observó usando un microscopio electrónico de transmisión (TEM). En general se obtuvo un buen grado de dispersión en los dos sistemas. La adición de nanotubos tuvo un efecto positivo en los nanocompuestos obtenidos ya que éstos exhibieron una alta conductividad eléctrica, una buena estabilidad térmica y una alta resistencia a la llama
Polybenzoxazines are considered a new type of thermosetting phenolic resins whose synthesis is quite simple. Polybenzoxazines present unique features that make them promising candidates for various industrial applications including electronics, aerospace, composites, coatings, adhesives, and encapsulants manufacturing. Two new benzoxazine materials have been synthesized and polymerized from the renewable diphenolic acid. The diphenolic acid-based benzoxazine (DPA-Bz) enables the preparation of rigid foams as well as flame retardant counterparts through a self-induced foaming process. For the methylester derivative benzoxazine (MDP-Bz), fiberglass reinforced materials were obtained with flame retardancy properties. Moreover, by adding neat carbon nanotubes, nanocomposite materials were prepared with low percolation threshold and improved thermal and fire properties.

The objectives of this project were to synthesise zeolites and aluminosilicate materials from silicon sources derived from biomass ashes. These materials will have great potential as catalysts and adsorbents. In order to begin this study it was necessary to find and optimise a technique for extraction of silicon to an alkali silicate solution from biomass ashes. It was then necessary to develop a technique for analysis of the alkali silicate solutions. This was done using calibration of integrals from infrared spectra. An optimisation of the synthesis of Zeolite X from a rice hull ash derived alkali silicate was developed and these materials were analysed and characterised using XRD, N2 Adsorption porosimetry, X‐Ray Fluorescence Spectroscopy, and X‐Ray Photoelectron Spectroscopy. An in‐depth study of the surface of the ash derived and reference Zeolite X was undertaken using in situ small molecule probing FT‐IR. It was found that although the materials were similar there was a significant difference due to the presence of a strongly bonded carbonate species in the pores of the bio‐derived zeolite. Synthesis of a Miscanthus ash derived mesoporous silica, MCM‐41, was successfully achieved which was comparable to its conventionally synthesised equivalent. Both displayed ordered hexagonal pores and high surface areas. A study on addition of different sources of aluminium found that it was possible to introduce aluminium into the structure successfully. Included in this study was the addition of the waste product ‘red clay’ as an aluminium source. Another mesoporous silica, SBA‐15 was synthesised from a Miscanthus ash derived alkali silicate. It was necessary to optimise the synthesis to adapt to the different pH systems of the conventional method and bio‐derived alkali silicate solutions. This was achieved and a bio‐derived SBA‐15 material with ordered hexagonal pores was produced.

With the ambition to decrease the utilization of fossil fuels, a development of those raw materials that today only are seen as waste products is necessary. One of those waste products is turpentine. Turpentine is the largest natural source of terpenes in the world today. The main components are the terpenes α-pinene, β-pinene and 3-carene.  In this project, different polymerisation techniques have been evaluated to polymerise limonene with the aim to make a material out of the green raw material, turpentine. Limonene is a terpene that can be found in turpentine. It has a planar structure and should work as a model for other terpenes.   Previous work on polymerising terpenes has focused on succeeding with performing polymerisations of terpenes utilizing the techniques of cationic polymerisation and radical polymerisation. However, this has been done without the aim to make a material out of the polymers. In this project, on the other hand, the main focus has been to obtain a polymer that can be used as a basis for a material. Techniques that have been applied are: radical polymerisation, cationic polymerisation and thiol-ene polymerisation.  In this study, attempts to homopolymerise limonene and also copolymerise it with other synthetic monomers, such as styrene, have been performed with both radical polymerisation and cationic polymerisation. The procedure for the radical polymerisation has been conducted following the work by Sharma and Srivastava. [1] Even though several articles have been published about radical copolymerisations of limonene with other synthetic monomers, the radical polymerisations have not succeeded in this project. Further, the technique of thiol-ene chemistry has shown that limonene can be used in polymerisations; limonene reacts spontaneously with 2-mercaptoethyl ether forming a viscous polymer. The obtained polymers have been characterized with proton nuclear magnetic resonance(1H-NMR), size exclusion chromatography (SEC), matrix-assisted laser desorption ionization-time of flight mass spectroscopy (MALDI-TOF MS), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy.

A robust method for the production of an emulsion polymer based on styrene-acrylic acid-acrylic ester was developed to give enhanced physical properties and/or reduced envhonmental impact. Replacing the methyl methacrylate content with n-butyl acrylate, tert-butyl acrylate and ethyl acrylate all gave stable polymer emulsions. Replacing methyl methacrylate with fatty acid based monomer containing no more than one polymerisable acrylate group per molecule also led to the production of a stable emulsion, with the fatty acid based monomer also acting as a self-emulsifying agent if having sufficient amphiphilic character. All stable emulsions were successfully used to produce composite materials.

The work presented in this thesis represents the chemical modification of waste and renewable vegetable oils to yield monomers for polyurethane, azide-alkyne click and nitrile-oxide click polymerisations. Chapter 1 provides a brief introduction to use of waste materials for new products, following on to a more detailed overview of triglyceride chemistry, finishing with an introduction to ‘Click’ chemistry. Chapter 2 discusses the optimisation studies of acid catalysed ring-opening of epoxidised cocoa butter followed by polyurethane synthesis. Percentage of ring-opening was found to be influenced by the amount of phase-transfer catalyst, concentration of reaction and equivalents of acid. Mechanical properties (Young’s Modulus (YM), Tensile strength (TS) and Elongation at break (EoB)) were determined and thermal analysis (TGA, DSC) measured on cocoa butter based polyurethanes both with and without food-safe dyes as an alternative more environmentally friendly renewable oil source for polyurethane synthesis. Chapter 3 focuses on the use of azide-alkyne click chemistry to produce renewable polymers from dimeric fatty amides (capable of H bonding) with increasing linker length and azide functionality. Samples were synthesised from purified oleic acid and linoleic acid and cheaper, more commercially available rapeseed oil and soybean oil. Thermal properties (TGA, DSC) of copper mediated and thermally produced polymers were analysed and mechanical properties (YM, TS and EoB) of thermally produced polymers were also investigated showing increasing linker length increased elongation and decreased tensile strength and also showed the importance of H bonding between polymer chains drawn. Chapter 4 expands on azide-alkyne click polymerisation by synthesis of a range of monomers containing both azide and alkyne units therefore capable of homopolymerisation. Increasing chain length, azide functionality and hydrogen bonding possibilities were again tested using the same four starting materials as Chapter 3 as well as increasing cross-linking possibilities and results were found to compare with those established in Chapter 3. Chapter 5 concentrates on using nitrile oxide-alkyne click polymerisations as an alternative and safe method of producing renewable polymers derived from vegetable oils. Two approaches were used for polymerisations, base mediated and thermal mediated polymerisations with polymers produced subjected to thermal analysis (TGA, DSC). Chapter 6 describes the experimental and chemical analysis of the key reactions and processes described in the thesis.

Thesis (M.S.)--University of California, San Diego, 2008.
Title from first page of PDF file (viewed June 12, 2008). Available via ProQuest Digital Dissertations. Includes bibliographical references.

The work in this thesis is concerned with growth of low dimensional materials in a variety of morphologies which have potential renewable energy generation applications. The work described within demonstrates synthesis methods for the production of materials with thermoelectric applications and materials for photovoltaic purposes. Products are characterised using a range of techniques including: scanning and transmission electron microscopy; energy dispersive X-ray spectroscopy and powder X-ray diffraction. Presented here is an investigation into the growth of bismuth telluride on silicon surfaces via chemical vapour deposition (CVD). Resultant particle morphology is reported in relation to experimental conditions such as surface conditions (silicon, gold/palladium on silicon and disordered silicon surfaces), temperature and reagent concentration. Successful synthesis of Bi2Te3 plates is presented starting from elemental precursors via a closed vessel CVD process. Plates with sub-micron thickness (but up to 40 μm diameter) are produced template free on a silicon surface and without the need for transport gases or expensive precursors. Using modification of silicon surfaces the growth of 2-4 μm tetragonal pyramids of Bi2Te3 are demonstrated. CVD is also used to produce bismuth rich nanowires up to 40 μm but <100 nm in diameter, these were produced by increasing the bismuth concentration in comparison to other methods. This thesis also details an investigation into the suitability of a range of substrates for CVD. Alumina is demonstrated to be a suitable surface for Bi2Te3 CVD with nanostructured Bi2Te3 spheres of 5-20 μm diameter presented. Additionally vertically aligned arrays of copper telluride are presented using a single step CVD process. Arrays consist of hexagonal plates <500 nm in thickness but up to 25 μm in diameter. Due to preferential reaction with tellurium GaAs is demonstrated to be a poor facilitator for Bi2Te3 growth as is cobalt. The production of nanostructured sphere of TiO2 is also presented. Spheres with tuneable diameter are produced in <60 s in multi-mode microwave reactors using a hydrothermal process. The spheres are comprised of radially aligned nanorods producing spheres of 1-3 μm. Spheres are demonstrated to be a single rutile TiO2 phase. Spheres are characterised with phase, band gap and morphology presented and influence of experimental parameters such as time and reagent concentration is discussed. 2 Finally this work investigates the doping and conversion of TiO2 structures to TiN and TiO2-xNx structures. Using ammonolysis TiO2 is converted to a TiN structure while retaining its original its original spherical morphology. Using the same ammonolysis process TiO2 is doped and the demonstrational shift in band gap to the visible region is presented.

Increasing requirements for renewable energy supply have pushed forward the development of low-cost, high-performance energy storage systems. Supercapacitors are a promising alternative to traditional electrochemical battery power storage devices as they have high power and energy densities and long cycle lives. Binary transition metal oxides (BTMOs) have been investigated as promising materials to improve supercapacitors as they can harness both faradaic and non-faradaic mechanism for energy storage and may exhibit improved conductance compared to simple metal oxides. The combination of these parameters leads to materials that can deliver superior capacitance, long cycling life, and good rate performance. Energy storage mechanisms in electrochemical devices are primarily surface reactions and maximising the available surface area for electrode/electrolyte interaction should improve storage capacity. As such, being able to create a porous electrode material with a suitable pore size distribution should improve the electrochemical performance of supercapacitors. The main aim of this work was to use polymeric templates to synthesise porous binary transition metal oxides (BTMOs) as a way of improving the specific capacitance of materials that could be used to construct supercapacitor electrodes. Novel, porous BTMO materials (NiMoO4, NiCo2O4, CoMoO4 and NaNiVO4) were synthesised using Egg-Shell Membrane (ESM) and poly(methylmethacrylate) (PMMA) using simple, one-pot hydrothermal combustion techniques. The synthesised materials were physically and electrochemically characterized. Addition of a template to the synthesis procedure resulted in improved performance compared to non-templated material for NiMoO4, NiCo2O4, and CoMoO4. In particular, use of the ESM template resulted in significant improvements in performance of the molybdates. The ESM templated NiMoO4 had the best performance with a measured specific capacitance 259 F.g-1 (2-electrode system) with an energy density of 252.2 Whkg-1. The ESM template seemed to promote the formation of β-NiMoO4, a crystal structure that has superior electrochemical storage properties compared to other isomorphs. This was achieved with relatively mild synthesis conditions and resulted in a material that had a porous structure consisting of nanowire like particles. This open, fibrous structure increased available surface area and accessibility to the interior of the bulk material. Optimal choice of polymeric template may need to be tuned to the final product as the best specific capacitances for CoMoO4 (74.45 F.g-1) and NiCo2O4 (38.03 F.g-1) were achieved using different templates; ESM for the former and PMMA for the latter. Synthesis of a novel material, NaNiVO4, was attempted but the resulting material was not fully characterised due to poor performance during initial electrochemical testing.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 204-211).
This thesis relates to the emerging field of high-throughput density functional theory (DFT) computation for materials design and optimization. Although highthroughput DFT is a promising new method for materials discovery, its practical implementation can be difficult. This thesis describes in detail a software infrastructure used to perform over 80,000 DFT computations. Accurately calculating total energies of diverse chemistries is an ongoing effort in the electronic structure community. We describe a method of mixing total energy calculations from different energy functionals (e.g., GGA and GGA+U) so that highthroughput calculations can be more accurately applied over a wide chemical space. Having described methods to perform accurate and rapid DFT calculations, we move next to applications. A first application relates to finding sorbents for Hg gas removal for Integrated Gas Combined Cycle (IGCC) power plants. We demonstrate that rapid computations of amalgamation and oxidation energies can identify the most promising metal sorbents from a candidate list. In the future, more extensive candidate lists might be tested. A second application relates to the design and understanding of Li ion battery cathodes. We compute some properties of about 15,000 virtual cathode materials to identify a new cathode chemistry, Li₉V₃(P₂O₇)₃(PO₄)₂ . This mixed diphosphate-phosphate material was recently synthesized by both our research group and by an outside group. We perform an in-depth computational study of Li₉V₃(P₂O₇)₃(PO₄)₂ and suggest Mo doping as an avenue for its improvement. A major concern for Li ion battery cathodes is safety with respect to 02 release. By examining our large data set of computations on cathode materials, we show that i) safety roughly decreases with increasing voltage and ii) for a given redox couple, polyanion groups reduce safety. These results suggest important limitations for researchers designing high-voltage cathodes. Finally, this thesis describes the beginnings of a highly collaborative 'Materials Genome' web resource to share our calculated results with the general materials community. Through the Materials Genome, we expect that the work presented in this thesis will not only contribute to the applications discussed herein, but help make high-throughput computations accessible to the broader materials community.
by Anubhav Jain.
Ph.D.

With increasing demand of renewable energy sources, electrochemical catalysts have attracted great attention as they are critically important for energy transformation devices such as fuel cell and metal-air batteries. Traditional high-performance electrocatalytic materials such as noble metal and noble metal-based oxides suffer from high cost and poor stability. To address this problem, other materials such as transition-metal-based compound-like oxides, chalcogenides, carbides, complexes and carbon-based materials have been considered and proven as promising candidates for alternatives to current noble metal-based electrocatalysts. This thesis attempts to develop high performance electrocatalysts based on earth abundant materials for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) process. To tackle the issues that limit the performance of such catalysts like poor electron conductivity, insufficient active sites and low mass transfer rate, various optimization methods were applied, including heteroatom doping, fabrication of porous structure and combining with a conductive substrate. Graphene, known as a star material, has been widely used in electrocatalysis because of its outstanding conductivity and large specific surface area. Extensive studies have been conducted to improve the catalytic performance of graphene-based materials. Generally, catalytic activity can be optimised in two methods: enhancing the intrinsic activity of the active sites and/or increasing the number of active sites. Both can be achieved at the same time. By chemically crafting diamino-benzene derivatives to ortho-quinone sites on holey graphene oxide (GO) edges via a simple condensation reaction, pyridinic nitrogen-decorated active sites for ORR can be obtained. The graphene-based electrocatalyst produced outperform Pt/C electrocatalyst in Zn-air batteries. This will be elaborated in Chapter 2. Transition metal-based compounds are also popular choices for electrocatalysts. A controllable synthesis method, developed to fabricate atomically thin CoSe2 nanobelt structures for water oxidation catalysis, will be discussed in Chapter 3. The as-synthesized material shows low overpotential, high current density, small Tafel slope and excellent catalytic stability, outperforming other assembled nano-structures. Furthermore, the electrode constructed from these nanobelts possesses a porous structure with highly accessible channels that allows facile electrolyte diffusion and efficient mass transfer. Spinel oxides are another class of material which also exhibits remarkable electrocatalytic activity. In Chapter 4, we investigated a series of Cobalt-doped spinel manganese oxide nanoparticles hybrid with GO nanosheets. The doping process alters the surface atomic arrangement and electronic property, which contribute to optimum adsorption behaviour of oxygen molecular and the ORR activities. When the dopant was 20 wt% (CMG-3), the doped material showed the best performance. The Zn-air battery assembled using CMG-3 as the air-cathode catalyst achieved good cycling performance at various current densities. Theoretical calculation is an effective tool for the design of catalyst and the exploration of the reaction mechanism. A study for low-dimensional metal-organic frameworks (MOFs) as HER catalyst was conducted. Using the Gibbs free energy of the adsorption of hydrogen atoms as a key descriptor, S atoms within one-dimensional MOFs are identified to be the preferred catalytic active sites for HER. The calculation results further revealed that the activities of part S atoms can be improved by interacting with alkali metal cations from the electrolytes; specifically, the influence of cations on the performance is dependent on the electron affinity of cations. This thesis highlight several achievements in developing earth abundant material-based electrocatalysts: (i) designing novel electrocatalysts based on the understanding of relevant mechanistic chemistry at the atomic level; (ii) developing facial synthetic routes for the preparation of earth-abundant carbon material, metal oxide and metal chalcogenide electrocatalysts; (iii) developing a surface doping approach to manipulate the surface electronic structure of metal catalysts; and (iv) evaluating the application potential of obtained material in Zn-air battery.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text

The present report is a reflection on the impact and costs of raw materials involved in renewable energy (RE) technology development. The study is performed in collaboration with ADEME in France and is based on a range of previous studies initiated by ADEME, which aimed to test the limits for the integration of renewables in the energy mix by considering their raw material consumption and identifying the possible impacts if this consumption steadily grows in the future.  The Earth’s material resources are already under heavy pressure, especially the exotic metals used in advanced technologies including renewable energy components and equipment. A sharp rise in material consumption due to a wide deployment of renewable energy could harm the metal markets and endanger the industries that depend on them. Securing a sustainable development path for RE technologies would require avoiding any fast resource depletion. This thesis focuses on several modern RE technologies, identifies their specific raw material consumption and points out some important strategic and economic issues regarding their sustainability. The possible penetration in the energy mix of France of different RE technologies related to their life-cycle and cost implications of the involved raw materials is discussed. The study also compares the requirement of raw materials for a 100%-RE energy system to a more conventional mix where the larger part is allocated to nuclear power and fossil fuels. By identifying the weaknesses and strengths of the renewable energy technologies as far as materials are concerned, the author aims at promoting the idea that a detailed Life Cycle Assessment of a project during the planning phase is a useful tool for the decision process and an important first step towards a more sustainable energy mix.

Emulsion polymerizations of vinyl acetate (VAc) were performed by fully or partially replacing poly(vinyl alcohol) (PVA) with renewable materials as protective colloids or by adding renewable materials, as additives or fillers, to the emulsions during or after polymerization. The purpose of the study was to increase the amount of renewable materials in the emulsion. A total of 19 emulsions were synthesized. Different recipes were used for the synthesis. The following renewable materials were studied; hydroxyethyl cellulose (HEC) with different molecular weights, starch and proteins. HEC and starch were used as protective colloids. Proteins were used as additives or fillers. Cross-linking agent A and Cross-linking agent B were used as cross-linking agents. A total of 26 formulations were pressed, either cold or hot. The synthesized emulsions were evaluated with respect to pH, solids content, viscosity, minimum film formation temperature (MFFT), glass transition temperature (Tg), particle size and molecular weight (Mw). The tensile shear strengths of the emulsions were evaluated according to EN 204 and WATT 91. It was possible to fully, or partially, replace PVA as protective colloid with renewable materials. It was also possible to use renewable materials as additives or fillers in the emulsions. The emulsions obtained properties that differed from the reference. Generally, emulsions with HEC as protective colloid showed lower viscosity and slightly higher MFFT, Tg and molecular weight than emulsions with PVA as protective colloid. Larger particle sizes than the reference were obtained for emulsions containing PVA combined with renewable materials. The emulsion with starch as protective colloid exhibited the largest particle size. 10 formulations passed the criteria for D2. The emulsions where PVA was fully or partially replaced with HEC or starch showed a water resistance similar to the reference (around D2). The addition of protein did not decrease the water and heat resistance compared to the reference. Addition of protein after polymerization increased the water resistance (D2) compared to addition during polymerization. Addition of cross-linking agents did not increase the water resistance further. Two formulations passed the criteria for D3. The emulsion in the first formulation had PVA as protective colloid and protein B was added during polymerization. The emulsion in the second formulation had HEC as protective colloid. To both of these emulsions, protein A was added after polymerization, as a filler, combined with Cross-linking agent B as cross-linking agent before hot pressing. The first formulation also showed a good heat resistance (passed the criteria for WATT 91).

La gestion des sources renouvelables est probablement l'un des enjeux majeurs du 21ème siècle. La part croissante de ces ressources intermittentes et fluctuantes telles que les énergies solaires, éoliennes et marines connectées au réseau électrique requiert des systèmes de stockage efficaces pour sécuriser et réguler l'approvisionnement électrique. L'objectif principal de cette thèse est donc la création de batteries aqueuses écologiques et durables à base de matériaux organiques à faible coût. En particulier, ce projet avait pour but d’identifier des stratégies pour synthétiser, comprendre et modifier des matériaux redox idoines pour en optimiser les réactions électrochimiques et chimiques. De plus, cette technologie a nécessité une mise en oeuvre particulière de ces matériaux mettant en jeu des électrodes millimétriques jamais réalisées à ce jour. Une nouvelle famille de molécules redox de type p/n a été identifiée. Leur comportement électrochimique, rationalisés par de nombreuses caractérisations physiques, a mis en évidence l’échange simultané de cations et d’anions ce qui n’a jamais été montré dans le domaine des batteries. En outre ce matériau permet une cyclabilité remarquable notamment dans l’eau de mer. La synthèse et le comportement électrochimique de différents dérivés du TEMPO en tant que matériaux actifs d'électrode positive ont également été évalués. Sur la base de ces découvertes des résultats très encourageants ont été obtenus avec les batteries aqueuses organiques complètes composées d'électrodes millimétriques
The management of renewable sources is probably one of the major issues of the 21st century. The increasing share of these intermittent and fluctuating sources such as solar, wind and marine energies connected to the electrical grid pushes towards the need for efficient storage systems to secure and regulate the supply of electricity. The main target of this thesis is therefore the creation of a low cost and sustainable full-organic aqueous cell. In particular, this project consisted in identifying strategies for synthesizing, understanding and modifying various organic redox materials to optimize their electrochemical and chemical behavior. In addition, the economic viability of this (new) technology required a particular implementation of organic materials according to industrially scalable processes, in millimeter thick electrodes ever made to date. As a result, a new p-/n-type redox active molecule and its electrochemical behavior in aqueous electrolyte has been presented. Further improvements have been achieved by modifying the previous compound into an oligomeric p-/n-type assembly which shows remarkable performance as cutting-edge negative electrode active material. This is the first redox material in the field of batteries able to exchange both anions and cations simultaneously. Extended cycling has been obtained in various electrolytes, including ocean water. The synthesis and the electrochemical behavior of different TEMPO derivatives as possible positive electrode active materials have been also evaluated. Finally, very encouraging results have been obtained by assembling full organic aqueous batteries composed of millimeter thick electrodes

The biological materials are the versatile scaffolds to fabricate functional nanomaterials. There is an increasing trend of applying the functional nanomaterials in energy applications ranged from conventional sources to renewables. In my early attempts of research, the M13 bacteriophage is used as a versatile bio-scaffold for the fabrication of nanomaterials. In this study, photocatalytically active perovskite strontium titanate (SrTiO3) nanowires are fabricated for the first time using genetically engineered AEEE–M13 phage and metal alkoxide precursors. One newly developed doping approach with an ammonia gas treatment efficiently produced strontium titanate nanowires, which split water and produce hydrogen under visible-light irradiation. The optical absorption of nitrogen doped strontium titanate can be tuned by varying the processing conditions, and lies in the visible spectrum range when treated at 625oC – 650oC. XPS results show that nanowires treated under ammonia flow between 625°C and 650°C have high nitrogen content. The excellent hydrogen evolution rate of these nanomaterials is correlated with both optical absorption and nitrogen doping level. This doping approach is expected to provide a new pathway for the fabrication of other visible-light active photocatalysts including tantalates. Beside to the anodic material, bismuth vanadium oxide (BVO4) nanowires as a cathode is synthesized in a similar method. This material is characterized by XPS, XRD, and TEM to confirm the formation of preferred crystallinity and size. The full reaction of water splitting has been tested by applying both materials and the initial results prove both nanowire materials can sustain for long time without any degradation while maintaining high performances. The electrocatalytic reduction of carbon dioxide by using SrTiO3 and TaON phage template nanowires is unique and innovative approach. Meanwhile, in the research, they have been proven to be more effective than any other bulk catalysts. Controlling the morphology and crystallinity of the electrocatalysts provides the new opportunities to produce various kinds of products including carbon monoxide, formic acid, methanol, ethanol, and methane. In research, we are capable to generate selective products by choosing the catalysts and varying the experimental conditions. Expended from the M13 bacteriophage bio-scaffold, a new biological functional nanomaterial is studied in my second project. DNA is biological ready-made sensor, and it is also small, customizable, and adaptive. The second project aims to develop new tools to improve the process of conventional energy extraction. More specifically, the research focuses to use functional nanomaterials to protect and delivery surfactants during the enhanced oil recovery (EOR). In order to recover hard-to-access oil, surfactants are pumped underground to help release the oil. The delivery area is large and it can take several weeks for the surfactant to reach the oil, which leads to dilution of and loss of the surfactant when it sticks to rocks. In order to improve the oil-to-surfactant yield, a controlled delivery method is of interest. In this project we are developing methods based on biological approaches for delivering surfactants to underground oil fields using nanoparticles that are stable for several weeks under high temperature and high salt conditions. We are using both biomimetic approaches mimicking structures such as diatoms and calcium based algae as well as genetic engineering to build high surfaces area biological sponges to act as surfactants. Motivated from previous project, the same microparticle system encapsulates various kinds of DNA is designed and fabricated for the underground detection to further improve the process of petroleum extraction. Inorganic microparticles containing various DNA segments were designed to be tracers that are used to identify the oilfield’s underground tunnel formations. CaCO3 is designed to encapsulate DNA nanoparticles. In order to prove the existence of DNA inside of particles after the synthesis, confocal imaging is taken on the fluorescence-label DNA particles, and the positive evidences of DNA that is inside of the particles is observed. After releasing the particle by dissolving the shell, the method of PCR is taken to amplify the DNA population and the gel electrophoresis is used to identify the size of DNAs. The same DNA strand that is initially encapsulated into the particle is confirmed as a result. Hence, it proves that the system of nanoparticle encapsulating the DNA is a successful application in the purpose as proposed. Many useful applications derived from the same encapsulation platform are studied and developed. More specifically, various DNA nanostructures are explored and encapsulated in the microparticles. The size control of microparticles is revisited to fulfill specific needs of the different applications. In addition, the particle buoyancy or density is engineered in order to improving the recyclability of the sensors from the aqueous media. The ability of encapsulation is also extended beyond various structures of nucleotide strands. In a few experiments, encapsulations of the gold nanoparticles and upconverting nanoparticles have been proven successfully. These extend the range of applications based on the functional materials inside that enable optical, biological, and environmental functions. Imaging techniques are improved to direct visualize the existence of specific structures. The adoption of typhoon provides a sensitive detection of low concentration of DNA. PAGE gel, compared to agarose gel that is introduced in previous chapter, is used to ensure a better separation among various structured macromolecules and hence a better resolution. DNA nanostructures act as the fundamental sensors responding to pH, ionization, and temperature changes. Learned many valuable insights from previous researches, with proper modifications, we propose new methods of fabricating sensors that allows people to detect the environments that currently no technology can do so.
Engineering and Applied Sciences - Applied Physics

Nearly 60 m tonnes of waste is produced annually in Europe from “plastic packaging” engendering significant challenges for legislative controls and minimisation of environmental impact. There is an increasing demand for biodegradable packaging, which can be disposed of with minimum environmental impact, but the growing market is still in its infancy predominantly due to a lack of materials having environmental, practical and economic suitability. This research project dealt with some processing challenges of environmentally friendly packaging materials from renewable resources, as a long term solution to mitigate some issues associated with oil based plastic packaging. In this work, novel Polylactic acid (PLA) and starch based composites were developed with the requisite technical properties to fill the gap in the food packaging and cosmetic packaging industry. It was found that starch can be incorporated in a PLA matrix at the 10% level without difficulty in processing in the presence of 2% methyldiphenyl diisocyante. The blend shows properties similar to pure PLA. It was also found that the elongation at break and impact properties of PLA can be increased remarkably by the addition of a biostrength impact modifier. Furthermore, mixing of PLA and starch in the blend is efficient when the PLA particle size is reduced. It was also found that flexible and tougher PLA/starch blend pellets, that can be injection moulded, can be produced by an extrusion process with a range of additives. Each additive has a maximum level that exhibits optimum properties. The blends also established that 15% starch can be incorporated into the PLA matrix to reduce the cost without any processing difficulties. Encouragingly, the presence of an impact modifier in the PLA/starch blends has shown more desirable properties. Furthermore, the mechanical properties of the pellets exposed to increased residence time in the injection moulding barrel and of the test specimens stored for 9 months at 21ºC were also satisfactory for the new blend. The overall results exhibited some attractive properties in the tri blend system, which can be easily adopted by the plastics industry for development of an injection moulded product within the scope of applications such as dry food packaging or cosmetic packaging. A further finding of this project is that biodegradation under a home composting environment can be improved by incorporating starch and certain other modifiers into PLA.

Le attività umane stanno progressivamente portando all'esaurimento delle risorse (limitate) del nostro pianeta e all'alterazione irreversibile degli ecosistemi, mettendo a rischio la qualità della vita delle generazioni future. Per questo motivo, mettere in pratica i principi della sostenibilità e dell'economia circolare, finalizzati – tra le altre cose – a minimizzare il consumo di risorse ed energia, i rifiuti e le emissioni, è diventato un tema cruciale nel mondo di oggi. Di conseguenza, il settore delle costruzioni è alla ricerca di soluzioni in grado di promuovere la sostenibilità e l'economia circolare senza penalizzare le prestazioni e la durabilità dei materiali da costruzione e delle infrastrutture, compresa l'adozione di materiali innovativi con ridotto impatto ambientale. A tal proposito, la nuova sfida nell'ingegneria dei materiali stradali è lo sviluppo e l'utilizzo dei cosiddetti “bio-leganti”, ovvero leganti in cui il bitume (che si ottiene dal petrolio) viene parzialmente sostituito con bio-materiali (soprattutto bio-oli) derivanti da residui o sottoprodotti da fonti rinnovabili (es. scarti del legno, biomasse vegetali non commestibili, letame animale, ecc.). Tuttavia, sebbene l'uso di bio-leganti nelle pavimentazioni stradali possa comportare significativi benefici ambientali, la conoscenza di questi materiali è ancora limitata, soprattutto in termini di prestazioni e durabilità. In questo contesto, questo progetto di dottorato (co-finanziato dall'azienda petrolchimica svedese Nynas AB) si è incentrato sulla caratterizzazione sistematica di laboratorio di bio-leganti ottenuti sostituendo parzialmente un bitume convenzionale con un bio-olio che è un residuo generato nella lavorazione di un sottoprodotto delle industrie della pasta di legno e della carta. Le prestazioni e la durabilità sono state valutate investigando diverse proprietà dei bio-leganti, tra cui la chimica, la morfologia, la reologia, la suscettività all'invecchiamento, l’adesione con aggregati lapidei, la suscettività all'acqua ed aspetti legati al riciclaggio. Nel progetto è stata inclusa anche la caratterizzazione delle prestazioni delle risultanti bio-miscele. I risultati ottenuti sono molto promettenti e suggeriscono che i bio-leganti possono essere considerati una valida alternativa ai tradizionali leganti bituminosi con potenziali benefici anche in termini di prestazioni e durabilità.
Human activities are progressively leading to the depletion of the (limited) resources of our planet and to the irreversible alteration of ecosystems, putting the quality of life of future generations at risk. For this reason, putting into practice the principles of sustainability and circular economy, aimed – among the other things – at minimizing resources and energy consumption, wastes and emissions, has become a crucial issue in today’s world. Consequently, the construction sector is looking for solutions that can promote sustainability and circular economy without penalizing the performance and durability of construction materials and infrastructures, including the adoption of innovative “green” materials. In this regard, the new challenge in road materials engineering is the development and use of so-called “bio-binders”, i.e. binders in which petroleum-based bitumen is partially replaced with bio-materials (especially bio-oils) deriving from residues or by-products from renewable sources (e.g. waste wood, non-edible vegetable biomass, animal manure, etc.). However, even though the use of bio-binders in road pavements would result in significant environmental benefits, the knowledge of these materials is still limited, especially in terms of performance and durability. Within this context, this PhD project (co-funded by the Swedish petrochemical company Nynas AB) focused on the systematic laboratory characterization of bio-binders obtained by partially replacing a conventional bitumen with a wood-based bio-oil that is a residue generated in the processing of a by-product from wood pulp and paper industries. Performance and durability were assessed by investigating several bio-binders properties, including chemistry, morphology, rheology, aging susceptibility, adhesion with aggregates, moisture susceptibility and recycling aspects. A performance-based characterization of the resulting bio-asphalt mixtures was also included in the project. The results obtained are very promising and suggest that the bio-binders can be considered a valid alternative to the traditional bituminous binders with potential benefits also in terms of performance and durability.

In this study, it is aimed to develop an innovative thermochemical energy storage system through material, reactor and process based investigations for building space heating applications. The developed system could be integrated with solar thermal collectors, photovoltaic panels or heat pumps to store any excess energy in the form of heat for later use. Thereby, it is proposed to address the problem of high operational costs and CO2 emissions released by currently used fossil fuel based heating systems in buildings. The aim of the study has been achieved by investigating and evaluating five of the following aspects: • Investigation of the feasibility of building integrated solar driven THS system under cold and mild climates, • Synthesis, characterization and physical experimentation of novel composite sorption energy storage materials • Development and investigation of a modular laboratory scale sorption reactor that use embedded air diffusers inside the sorbent for improving the energy storage density • Development and investigation of a full- scale modular solar driven THS system • Development and investigation of a heat pump driven sorption storage heater using multi-layer fixed bed sorption reactor These works have been assessed by means of computer simulation, laboratory and field experimental work and have been demonstrated adequately. The key findings from the study confirm the potential of the examined technology. Initially, a comprehensive review on thermal energy storage, with the aim of investigating the latest advancements on THS systems was performed. A comparative analysis on applicability of different heat storage methods for short term and seasonal heat storage under climate conditions in the UK, was also carried out. Results showed that short term heat storage is not a feasible option in the UK due to the very limited solar radiation. For the case of seasonal heat storage, it was found that, each 1 m3 of THS can provide averagely 14% of monthly (October to March) heating demand of a 106 m2 building, whereas LHS and SHS can provide 6% and 2% respectively. Later on, a range of candidate composite sorption materials were synthesized and characterized. Based on the applied characterization techniques, it was found that Vermicuilite-CaCl2 (SIM-3a) has excellent Ed coupled with good EMC and temc with its TGA analysis also suggesting significant mass loss in the working range 30 < T < 140 °C. Physical experimentation of the developed materials in a small scale custom test rig was also performed and in accordance with the characterization results, SIM-3a displayed the best hygrothermal and cyclic performance. These findings suggested that SIM-3a has very good potential for use in an open THS system. Upon completion of the material based studies, a 3kWh laboratory scale novel reactor using perforated pipes embedded inside the heat storage material was developed. The overall energy density of the reactor using SIM-3a was found 290 kWh/m3. Based on the obtained encouraging results, same concept was up scaled to a modular 25 kWh sorption pipe heat storage and similar energy density was achieved. Following the experimental work, theoretical analysis of the THS potential in Mediterranean climate conditions is conducted with a case study of the Island of Cyprus. The analysis results showed that the required heat storage volume to fully compensate heating demand of a domestic building in winter (December to February) is 5.25 m3 whilst the time required for charging the THS material with 8 m2 solar air collectors is slightly more than a month. The economic and environmental analyses results showed that payback period of the solar driven THS is 6 years whilst total CO2 emissions savings over 25 years lifetime is 47.9 tonnes. In order to validate the applicability of THS in Cyprus, a small prototype of integrated sorption pipe-solar concentrator was also developed and tested for room heating. It was found that adsorbent could be regenerated with solar energy during winter day time to be utilized at night for space heating. Study results also showed that sorption pipe with a heat storage volume of 0.017 m3 could meet up to 87% of the daily heat demand of a 12.4 m2 building. In order to validate the performance of the laboratory tested THS material and concept, a real scale (1000 kWh) modular solar driven THS system was developed based on the interpretation of the obtained theoretical, numerical and experimental data in earlier stages of the study. The preliminary testing on the prototype showed that each of four reactors could discharge a total of 248 kWh of thermal energy with an average thermal power of 4.8 kW. Additionally it is found that, in direct solar heating mode, transpired solar collectors used in the system could also generate daily total of 17 kWh thermal energy for the average solar intensity of 0.3 kW/m2. In the final stage of the study, a heat pump driven sorption storage heater was developed and investigated. The developed system performance was assessed with 5 different adsorption materials and under different operating conditions. The study results showed that Sim-3a and Vermiculite–(LiCl-CaCl2) (Sim-3cl) has the best hygrothermal performances and hygro-cyclic efficiencies. According to study results, COPs varies in the range of 1→2 depending on sorption materials properties and system operating conditions.

The development of green and efficient electrocatalysis, which targets the generation and storage of renewable energy by transforming electrical energy to chemical energy, is strongly driven by the challenges we face in increasing energy demand. Consequently, great efforts have been made in exploring efficient electrocatalysts. The conventional trial-and-error approach for electrocatalysts is timeconsuming due to the lack of direct information regarding the atomic-scale properties of electrocatalysts and the underlying elementary reaction mechanisms. To date, the rational molecular design of high-performance electrocatalysts has been extensively used. However, most of these computational studies are still in their infancy and more reliable modelling of electrochemical processes is needed to bridge the gap between experiments and theory. This thesis aims to utilize structural engineering at the atomic scale to develop high-performance electrocatalysts for hydrogen evolution reaction (HER) and chlorine evolution reaction (CER), and model the external factors of the operating environment to provide a better description of electrocatalytic processes. The general background and objectives of this PhD project are presented in Chapter 1. The recent progress in numerical modelling of electrochemical reactions and processes is discussed in Chapter 2. The importance of theoretical identification and understanding of catalytic active sites is highlighted in this chapter. The computational method employed in this project is the density functional theory (DFT), which has been demonstrated to achieve increasing success in the description and understanding of the II complexity of electrocatalysis. Chapter 3 provides a short introduction of the DFT method, including its origin, development, and implementation. Chapters 4-7 present all the research work completed for this project. As metalorganic frameworks (MOFs) are considered a large family of low-dimensional materials, a comprehensive computational study was conducted to investigate the structural properties and electronic properties of one-dimensional (1D) transition metalbased dithiolene MOFs. Their high electrical conductivities offer the potential for electrocatalytic hydrogen evolution, which is examined with the consideration of electrolyte effects in Chapter 4. As the one of main industrial reactions, CER electrolysis is challenging due to the selectivity of Cl2. This can be ascribed to the unavoidable oxygen evolution from the noble metal-based dimensionally stable anodes (DSAs) used in industry. To this end, six TMN4 complex embedded graphene (TMN4@G) single-atom catalysts (SACs) were systematically investigated in Chapter 5. The DFT results predicted that NiN4@G is a promising candidate for efficiently and selectively catalyzing chlorine evolution in acidic solution. Chapter 6 theoretically studied the performance of CER for eight two-dimensional (2D) semiconducting group- VA monolayers with α and β phases. It is suggested that β-arsenene monolayer exhibits high activity and selectivity of gaseous Cl2 generation by virtue of the expected Cl* precursor. In Chapter 7, three low-dimensional Fe/Co/Ni−dithiolene MOFs were purposely selected due to their acid resistance and comprehensively investigated for electrocatalytic CER. The calculated results demonstrate that Ni-based dithiolene MOF can efficiently catalyze the CER via the Cl* pathway. This thesis makes significant contributions to the theoretical understanding of electrochemical processes, materials science, and electrochemical energy conversion and storage through: (i) demonstrating the importance of electronic configurations of metal cations in the electrical conductivities of transition metal-dithiolene MOFs; (ii) proposing a novel strategy for optimizing the electronic structure of materials on the basis of the resonant charge transfer mechanism; (iii) predicting efficient lowdimensional electrocatalysts for Cl2 evolution with the Cl* intermediate rather than the ClO* intermediate; and (iv) investigating the interactions between adsorbates and catalysts to provide a new descriptor for the discovery of high-performance CER electrocatalysts. It is worth noting that the studies on the electrocatalytic properties of low-dimensional materials are still in the early stage. As such, more accurate models and approaches combined with multiscale simulation are needed in future studies, such as the modelling of the electrode-electrolyte interface, dynamic solvent, and electrical double layer.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Full Text

The  strive  to  minimize  emissions  in  the  automotive  industry  keeps gaining momentum. Continuous improvement of engine designs and development of more efficient  fuel  systems  in  diesel  vehicles  is  a  solution to  be  applauded.  More importantly is the growing shift to use of renewable fuels in internal combustion engines.  With  countries  implementing  tighter regulations  on  emissions,  and markets  have  witnessed  a  rise  in  the  use of  biofuels.  Subsequently, the fuel quality varies from market to market. Blending  of  different  fuels  changes  the properties  of  fuel  as  solubility  of some  compounds  reduce.  Consequently,  soft particles  which  are precipitated  in  the  process  have  been  linked  to  deposit formation of internal diesel injector deposits (IDIDs). This project aims at investigating IDIDs and possible conditions that enhance their  formation  in  the  injector.  An injector test rig operating at actual engine pressures (>2000 bars) has been constructed for this purpose.  Test fuel for use in the rig is prepared at Scania by introducing soft particles into B10 fuel. Start of the test rig was performed by checking component functionality and pressure test. Due to leakage problem, a redesign of fuel collection cup was done. Evaluation of test fuel  was  carried  to  determine  the  suitability  for deposit  formation  in  the injector. Two screening tests were carried to investigate sticky deposit formation using the test fuel. Autoclave test was carried out at temperature of 150 0C over a period of up to four days. Frying pan test was performed to evaluate formation of deposits with increase in temperature between 90 0C to 230 0C. Analysis was carried out using SEM-EDX, GC-MS and FTIR instruments. The test fuel prepared at Scania for replication of deposits in the injector yielded positive results. Sticky deposits formed during the frying pan test evidenced by stretchy and sticky residue on the pan. FTIR analysis showed that the presence of metal carboxylate which is as a result of the metal ion soft particles. Autoclave tests showed formation of brown deposits on the vessel. SEM-EDX analysis of the brown deposits gave great insights on the morphology of the deposit contrasted to the structure of soft particles initially present in the test fuel. Soft particles are small and smeary with a regular shape while the deposits are large, irregular, agglomerated and rough in texture.  This is important in understanding the transformation mechanism of soft particles to deposits. A combination of calcium and sodium soft particles in the test fuel showed better ability to form deposits during   the   autoclave   test.   GC-MS   analysis   showed   huge   decrease   in   the concentration of soft particles in test fuel after autoclave tests compared to initial test fuel. In conclusion, the test fuel prepared works as expected and thus can be scaled up for running the injector test rig. Additionally, test fuel containing calcium and sodium soft particles have a higher probability to form deposits. Deposits were indeed proven to be metal carboxylates as expected.
Strävan efter att minimera utsläppen inom fordonsindustrin fortsätter att ta fart. Kontinuerlig förbättring av motorkonstruktioner och utveckling av effektivare bränslesystem i dieselfordon är en lösning som bör applåderas. Ännu viktigare är den ökande övergången till användning av förnybara bränslen i förbränningsmotorer. Med länder som inför strängare utsläppsregler har marknaderna sett en ökad användning av biobränslen. Därefter varierar bränslekvaliteten från marknad till marknad. Blandning av olika bränslen förändrar bränslets egenskaper när lösligheten hos vissa föreningar minskar. Följaktligen har mjuka partiklar som fälls ut i processen kopplats till avlagringsbildning av interna dieselinjektoravlagringar (IDID). Detta projekt syftar till att undersöka IDID:s och möjliga förhållanden som förbättrar deras bildande i injektorn. En injektortestrigg som arbetar vid faktiska motortryck (>2000-bar) har konstruerats för detta ändamål. Testbränsle för användning i riggen bereds på Scania genom att mjuka partiklar förs in i B10- bränsle. Testriggens start utfördes genom kontroll av komponentens funktionalitet och trycktest. På grund av läckageproblem gjordes en omdesign av bränsleuppsamlingskoppen. En värdering av testbränslet genomfördes för att fastställa lämpligheten för deponeringsbildning i injektorn. Två screeningtester utfördes för att undersöka klibbig avlagringsbildning med hjälp av testbränslet. Autoklavtest utfördes vid en temperatur av 150 C under en period av upp till fyra dagar. Autoklavtest utfördes för att utvärdera bildandet av avlagringar med temperaturökning mellan 90 0C till 230 C. Analysen utfördes med hjälp av SEM-EDX, GC-MS och FTIR instrument. Testbränslet som förbereddes i Scania för replikering av avlagringar i injektorn gav positiva resultat. Klibbiga avlagringar som bildas under stekpannans test framgår av stretchiga och klibbiga rester på pannan. FTIR-analys visade att förekomsten av metallkarboxylat som är ett resultat av metalljonens mjuka partiklar. Autoklavtester visade bildandet av bruna avlagringar på fartyget. SEM-EDX-analysen av de bruna avlagringarna gav stora insikter om depositionens morfologi i motsats till strukturen hos mjuka partiklar som ursprungligen fanns i testbränslet. Mjuka partiklar är små och utsmetade med en regelbunden form medan avlagringarna är stora, oregelbundna, agglomererade och grova i konsistensen. Detta är viktigt för att förstå omvandlingsmekanismen för mjuka partiklar till avlagringar. En kombination av kalcium- och natriummjuka partiklar i testbränslet visade bättre förmåga att bilda avlagringar under autoklavtestet. GC-MS-analysen visade en enorm minskning av koncentrationen av mjuka partiklar i testbränsle efter autoklavtester jämfört med det ursprungliga testbränslet. Sammanfattningsvis fungerar testbränslet som förväntat och kan därför skalas upp för att driva injektortestriggen. Dessutom har testbränsle som innehåller mjuka kalcium- och natrium partiklar större sannolikhet att bilda avlagringar. Avlagringarna visade sig faktiskt vara metallkarboxylater som förväntat.

Plant derived oils bear intrinsic double-bond functionality that can be utilized directly for the thiol–ene reaction. Although terminal unsaturations are far more reactive than internal ones, studies on the reversible addition of thiyl radicals to 1,2-disubstituted alkenes show that this is an important reaction. To investigate the thiol–ene coupling reaction involving these enes, stoichiometric mixtures of a trifunctional propionate thiol with monounsaturated fatty acid methyl esters (methyl oleate or methyl elaidate) supplemented with 2.0 wt.% Irgacure 184 were subjected to 365-nm UV-irradiation and the chemical changes monitored. Continuous (RT– FTIR) and discontinuous (NMR and FT–Raman) techniques were used to follow the progress of the reaction and reveal details of the products formed. Experimental results supported by numerical kinetic simulations of the system confirm the reaction mechanism showing a very fast cis/trans-isomerization of the alkene monomers (<1.0 min) when compared to the total disappearance of double-bonds, indicating that the rate-limiting step controlling the overall reaction is the hydrogen transfer from the thiol involved in the formation of final product. The loss of total unsaturations equals thiol consumption throughout the entire reaction; although product formation is strongly favoured directly from the trans-ene. This indicates that initial cis/trans-isomer structures affect the kinetics. High thiol–ene conversions could be easily obtained at reasonable rates without major influence of side-reactions demonstrating the suitability of this reaction for network forming purposes from 1,2-disubstituted alkenes. To further illustrate the validity of this concept in the formation of cross-linked thiol–ene films a series of globalide/caprolactone based copolyesters differing in degree of unsaturations along the backbone were photopolymerized in the melt with the same trithiol giving amorphous elastomeric materials with different thermal and viscoelastic properties. High thiol–ene conversions (>80%) were easily attained for all cases at reasonable reaction rates, while maintaining the cure behaviour and independent of functionality. Parallel chain-growth ene homopolymerization was considered negligible when compared with the main coupling route. However, the comonomer feed ratio had impact on the thermoset properties with high ene-density copolymers giving networks with higher glass transition temperature values (Tg) and a narrower distribution of cross-links than films with lower ene composition. The thiol–ene systems evaluated in this study serve as model example for the sustainable use of naturally-occurring 1,2-disubstituted alkenes at making semi-synthetic polymeric materials in high conversions with a range of properties in an environment-friendly way.
Vegetabiliska oljor som innehåller dubbelbindningar kan användas direkt för thiolene reaktioner. Trots att terminala dubbelbindningar är mycket mer reaktiva än interna visar dessa studier att den reversibla additionen av thiyl radikaler till 1,2-disubstituerade alkener är en viktig reaktion. För att undersöka tiol–ene reaktionerna, som ivolverar dessa alkener förbereddes stökiometriska blandningar av en trifunktionell propionat tiol och enkelomättade fettsyrametylestrar (metyloleat eller metyl elaidat) samt 2.0 vikt.% Irgacure 184. Dessa blandningar utsattes för 365-nm UV strålning och de kemiska förändringarna studerades. De kemiska förändringarna analyserades med olika kemiska analysmetoder; realtid RT–FTIR, NMR och FT–Raman. Dessa användes för att analysera de kemiska reaktionerna i realtid och följa bildandet av produkterna. Reaktionsmekanismen bekräftades med hjälp av experimentella data och beräkningar av numeriska och kinetiska simuleringar för systemet. Resultaten visar en mycket snabb cis/trans-isomerisering av alkenmonomeren (<1.0 min) jämfört med den totala förbrukningen av dubbelbindningarna, vilket indikerar att det hastighetsbegränsande steget kontrolleras av väteförflyttningen från tiolen till slutprodukten. Förbrukningen av den totala omättade kolkedjan är lika med tiolförbrukningen under hela reaktionen, även om bildandet av produkten gynnas från trans-enen. Detta indikerar att den första cis/trans-isomerstrukturen påverkar kinetiken. Höga tiol-ene utbyten kan enkelt erhållas relativt snabbt utan inverkan av sidoreaktioner. Detta innebär att denna reaktion kan användas som nätverksbildande reaktion för flerfunktionella 1,2-disubstituted alkenmonomerer. Vidare användes fotopolymerisation i smälta på en serie globalid/kaprolaktonbaserade sampolyestrar med varierad grad av omättnad med samma tritiol vilket resulterade i bildandet av amorfa elastomeriska material med olika termiska och viskoelastiska egenskaper. Hög omsättning (>80%) uppnåddes relativt enkelt för samtliga blandningar oberoende av den initiala funktionaliteten. Homopolymerisation av alkenen var försumbar i jämförelse med den tiol–en-reaktionen. Mängden alkengrupper har inverkan på härdplastsegenskaperna där en hög andel alken ger en nätstruktur med högre glastransitionstemperatur (Tg). Tiol–ene reaktionen utvärderades i modellsystem baserade på naturlig förekommande 1,2-disubstituterade alkener för att demonstrera konceptet med tiol-förnätade halvsyntetiska material.
QC 20110915

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 181-193).
Modulation of a material's dimensionality enables novel physics at the atomic scale. Exploiting this effect creates opportunities to design and manufacture highly functional materials for specific engineering applications. As such, 2D materials are an exciting material group due to their unique properties compared to their 3D counterparts. Currently, research is focused on understanding how these low dimensional materials can perform as photovoltaics, catalysts, and high strength materials. The first goal of this thesis is to understand and design the properties of complex 2D materials for novel applications in renewable energy. The second goal is to develop new methods that will enable accurate and efficient investigation of the fundamental electronic structure properties of these and other complex materials. In this thesis, we study the underlying physics of an exciting class of materials broadly referred to as transition metal phosphates (TMPs). These materials are of interest for engineering applications because of their 2D properties, ease of solution processing, and ability to form 2D monolayers. Interestingly, they form crystalline materials composed of alternating layers of TMPs and organic molecules, enabling a wide range of material properties. Additionally, TMPs exist in a variety of compositions including zirconium, titanium, vanadium, zinc, tin, and a number of other metal cations. This range of cations presents an opportunity to study a rich set of properties and potential applications within the framework of TMPs. To study these materials, we employ density functional theory (DFT) computations to investigate the properties of TMPs and TMP-based heterostructures. Using DFT, we develop a framework for the understanding and control of the band gap, band alignment, and other properties within TMP-organic heterojunctions. This work enables new pathways for the realization of cheap and efficient photovoltaic materials as well as applications to broader engineering fields concerned with precise control of band energies. In performing this study, we also address several critical limitations of DFT. While DFT is highly accurate at studying many materials properties, it has significant limitations in studying time variant and excited-state properties. Further, computationally, DFT does not scale linearly with the system size, imposing significant roadblocks to study large systems. To enable the study of these complex material properties, method development represents a significant portion of this work. Artificial neural network (ANN) approaches represent an emergent method in the field of Material Science. Exploiting this trend, we develop ANN methods to reduce the computational complexity and cost of DFT simulations. By combining large datasets of relatively small DFT calculations, we develop high dimensional potentials for large-scale molecular dynamics (MD) calculations. This enables the prediction of DFT-accurate energies in large and time-variant systems for a fraction of the computational cost. Additionally, DFT relies on accurately understanding the relationship between functionals of the charge density even though the explicit form of some functionals are sometimes unknown. To address this shortcoming of DFT, we develop machine-learning methods as a novel way to learn complex functionals. Understanding this process may allow for linear speedup in DFT calculations, possibly opening enabling 'orbital-free' DFT. In concluding this thesis, we deploy our computational framework to learn both analytical potentials as well as functionals of the charge density. We use these developed methods to study a range of material properties of interest to the engineering sciences including the bandgap and mechanical properties of 2D and bulk materials. This method could enable significant advances in the computational material science field by enabling researchers to study systems not possible with classical approaches.
by Levi Carl Lentz.
Ph. D.

Climate change and renewable energy have recently become part of the school curriculum in South Africa. Many teachers at the secondary school level thus have to teach topics with which they are not (necessarily) familiar. The Centre for Renewable and Sustainable Energy Studies at Stellenbosch University has established a schools' programme to provide materials to aid the educators in the teaching of renewable energy topics. A research-based set of Learning Teaching Support Material (LTSM) was developed for high school educators. The learning material includes a DVD, PowerPoint presentations, posters, a teacher's manual, and assignments that can be used in different subjects. This study reports and reviews how teachers are currently using the material. Teacher accounts of materials use and evidence of learning in students work were solicited using an appreciative inquiry review process. The data reflected the value being created through patterns of materials use. A Vygotskian based task sequencing framework of Anne Edwards was used to examine the patterns of use which support learning. The use of the task sequencing as an analytical lens allowed the review to probe how knowledge representation was the primary use by teachers. Here they introduced learners to key concepts and to broaden their knowledge on renewable energy. The activities served to scaffold a clear learning progression but the activities were not strongly enough orientated towards ESD as learner-led processes of enquiry and action. The outcomes of the study will be used to update and better align the materials with a need for teachers to strengthen important ESD outcomes in the current curriculum.

The work presented in this thesis reports the development of a non-stick coating for bakeware from renewable materials. Also investigated is the use of epoxidised vegetable oils for renewable polyesters and nanocomposites. Chapter 1 provides a brief introduction to materials from renewable sources leading to a more detailed overview of triglyceride chemistry and finishes with a brief background of non-stick coatings. Chapter 2 presents the development of the non-stick coating. Current commercial coatings were analysed identifying the key components that could be replaced with more environmentally friendly alternatives. Thermal and photo-initiated curing regimes were studied on a range of epoxidised vegetable oil monomers for use as a polymer binder. Thermally cured epoxy soybean oil using a sulfonic acid catalyst was deemed superior. Additives to this resin such as silica, pigments and solvents were investigated to produce a coating formulation which was analysed by TGA and industry standard surface tests including pencil hardness, flexibility and cross-hatching. Chapter 3 reports the hydrosilylation reaction on vegetable oils. A model system with fatty acids and triethylsilane was proposed which lead to the formation of crosslinked silicone rubbers using di- and polyfunctional silanes and vegetable triglycerides. Epoxy fatty acid – silicone hybrids were used as release agents in the non-stick coating formulation described above. Chapter 4 focuses on the ring opening polymerisation of epoxidised vegetable oils with cyclic anhydrides forming crosslinked polyesters. Mechanical properties such as tensile strength, elasticity and Young’s modulus were measured as well as thermal analysis (TGA, DSC and DMTA). It was found that the physical properties were related to the crosslinking density with a higher density lead to strong but brittle polymers whereas lower crosslinking density samples were soft and elastic. The crosslinking density could be controlled by the choice of the vegetable oil type, anhydride type and the epoxide : anhydride ratio. Chapter 5 uses these polyester resins in the formation of nanocomposites. Nanocomposites were created using hollow silica shells and polyaromatic hydrocarbons and the mechanical properties measured and compared to the vegetable oils resins alone and other work in this area. This was followed by the copolymerisation of epoxy vegetable oils and styrene oxide and blends of grapessed and euphorbia oils with different epoxide functionality. It was found that blends could achieve properties of both oils such as high strength and elasticity in the same polymer sample. Chapter 6 describes the experimental procedures and chemical analysis of reactions performed in this thesis.

Global plastic pollution of the natural environment is extremely detrimental as it is causing deaths of animal species. More than 80 % of marine litter is made up by plastics and 70 % of those are made up by disposable items. For this reason, the European Parliament has agreed to abolish the top ten single-use plastic items found in the marine environment from the EU market from 2021. Therefore, the fossil-based disposables will need to be substituted by disposables made from renewable materials. It is thus important to investigate the environmental impact of these alternatives through their life cycle in order to support sustainable consumption and production. In this study, environmental impact of disposable plates made from two different renewable materials (paper and leaf) were analysed by means of life cycle assessment (LCA). The aim of the study was to examine the environmental performance of the two plates in the impact category global warming potential (GWP); and reveal the processes with the largest contributions to the overall GWP of each plate. The leaf plate was produced in India and the paper plate in the Nordics, however, both plates were used and disposed of in Uppsala, Sweden. The results showed that the leaf plate has a higher GWP due to its long-distance transport and electricity use derived from fossil fuels. Scenario analysis has proved that its GWP can be reduced when sea transport route is chosen instead of flying and production is increased. When it comes to the paper plate life cycle, the processing stage was identified to contribute the most to the total GWP. It could be further improved by applying a biodegradable layer for its coating. To keep the good performance in GWP the plate should be incinerated with energy recovery. The disposal of the plates has a substantial positive influence on their total carbon footprint as both plates substitute use of fossil fuels. However, the credits allocated for the different waste management options are specific to Uppsala and thus the results of this study should be applied only under similar conditions.

Developing renewable materials to reduce the dependence on fossil fuel as a feedstock for a wide range of applications is becoming increasingly acknowledged as important in society. Chitin, the second most abundant biopolymer in nature, is an ideal candidate for diverse applications because of its remarkable properties, such as abundance, renewability, biodegradability, biocompatibility, antibacterial activity, chemical functionality, and high stiffness and strength. Despite these inherent advantages, chitin is currently still underutilized mainly due to its strong molecular interactions, which make it insoluble in common solvents. Currently, its major applications are limited to biomedical engineering, such as tissue engineering, wound dressing and sutures. This thesis aims to explore and enable the potential utilization of chitin in other fields where it may serve as a renewable functional advanced material. Here, a number of novel chitin-based materials were developed successfully without employing chitin dissolution. These include chitin nanofibers (CNFs), porous chitin with tunable structures, chitin-reinforced polymer composites and chitin-stabilized aqueous foams. Moreover, the properties of these materials including interfacial, optical, thermal, and mechanical characteristics were determined, and their potential utilizations were demonstrated. Briefly, in chapter 2, CNFs with diameters of ~20 nm were successfully extracted from crab α-chitin by a high pressure homogenization process. The produced CNFs were dispersed well in water without forming strong network structures due to their electrostatic repulsions. The obtained CNF film has a high residue amount (40%) when heated up to 1000 ˚C. Meanwhile, it exhibited high optical transparency as well as great gas barrier properties. In chapter 3, on the basis of the obtained CNFs in chapter 2, versatile porous structures including oriented sheets and three-dimensional aperiodic nanofiber networks were achieved by using a freeze drying technique. Since the formation of nanofibrous structures cannot be predicted by the widely-used particle encapsulation model, a modified structure formation mechanism was proposed. In chapter 4, the structure-property relationships of the CNF/poly(ethylene oxide)(PEO) nanocomposites were established. We demonstrated that the CNFs formed network structures in PEO matrix and had hydrogen bonding interaction with PEO. The CNFs can greatly enhance the mechanical properties of PEO, such as elastic modulus and tensile strength. In chapter 5, the aqueous foams stabilized by high-aspect-ratio CNFs were developed. The created foams exhibited strong hindrance on film drainage, coalescence and disproportionation. The fibrillated CNFs alone were not able to stabilize air bubbles, but the addition of small amounts of valeric acids in CNF dispersion can make chitin foamable. The results clearly showed that valeric acid modified CNFs reduced the surface tension of aqueous dispersion and were attached at the air-water interface. Overall, this research has provided many new insights for the fabrication, characterization, and utilization of chitin, and has built a solid foundation for further exploiting chitin for diverse applications.

Intermittent nature of renewable energy sources like the wind and solar energy poses new challenges to harness and supply uninterrupted power for consumer usage. Though, converting energy from these sources to useful forms of energy like electricity seems to be promising, still, significant innovations are needed in design and construction of wind turbines and PV arrays with BS systems. The main focus of this research project is mathematical modelling and control of wind turbines, solar photovoltaic (PV) arrays and battery storage (BS) systems. After careful literature review on renewable energy systems, new developments and existing modelling and controlling methods have been analysed. Wind turbine (WT) generator speed control, turbine blade pitch angle control (pitching), harnessing maximum power from the wind turbines have been investigated and presented in detail. Mathematical modelling of PV arrays and how to extract maximum power from PV systems have been analysed in detail. Application of model predictive control (MPC) to regulate the output power of the wind turbine and generator speed control with variable wind speeds have been proposed by formulating a linear model from a nonlinear mathematical model of a WT. Battery chemistry and nonlinear behaviour of battery parameters have been analysed to present a new equivalent electrical circuit model. Converting the captured solar energy into useful forms, and storing it for future use when the Sun itself is obscured is implemented by using battery storage systems presenting a new simulation model. Temperature effect on battery cells and dynamic battery pack modelling have been described with an accurate state of charge estimation method. The concise description on power converters is also addressed with special reference to state-space models. Bi-directional AC/DC converter, which could work in either rectifier or inverter modes is described with a cost effective proportional integral derivative (PID/State-feedback) controller.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on February 12, 2010). Thesis advisor: Dr. Galen J. Suppes. Includes bibliographical references.

This research focuses on the synthesis and development of new functional nanomaterials with tailored morphology for high performance supercapacitors and hydrogen generation through electrolysis of water splitting in order to alleviate the energy crisis and environmental problems. A series of nickel based nanomaterials have been synthesized and their electrochemical properties were thoroughly studied. Ultrafine amorphous barium nickel phosphate nanofibers, and Ni-Co and NiCu layered double hydroxide (LDH) nanosheet arrays directly grown on carbon fibre clothes (CFC) demonstrated excellent performance for supercapacitors while NiCoFe LDH nanosheet arrays on CFC showed high catalytic activity for oxygen evolution reaction for water splitting.

The world is facing a major challenge when it comes to proper energy utilization. The increasing energy demand, the depleting fossil fuel resources and the growing environmental and ecological concerns are factors that drive the need for creative solutions. Renewable energy resources such as solar sit in the center of these solutions. Due to their intermittent nature, development of energy storage systems is crucial. This dissertation focused on the latent thermal energy storage systems that incorporate phase change materials (PCM). The main goal was to enhance the heat transfer rates in these systems to address the low melting (energy storage stage) and solidification (recovery stage) rates that are caused by the PCMs’ low thermal conductivity values. The application of multiple PCMs (m-PCMs) with varying melting temperatures in several arrangements was investigated. The effects of applying m-PCMs on the conduction heat transfer and on the natural convection heat transfer in both horizontally and vertically oriented heat exchangers were studied. This was followed by an optimization study of the PCMs’ melting temperatures and the working fluid flow rate. Further heat transfer enhancement using metal fins was also investigated. Numerical models were developed and validated. Results are reported and discussed. Significant enhancement in both complete melting time and energy storage capacity was obtained by the m-PCMs in series arrangement. This enhancement is more pronounced in the vertically oriented system. The working fluid flow rate was found to have a limited effect during the melting stage. However, it seems to be crucial in the solidification stage.

Organo-metallic halide perovskite solar cells (PSCs) are considered as a promising alternative photovoltaic technology due to the advantages of low-cost solution fabrication capability and high power conversion efficiency (PCE). PSCs can be made using a conventional (n-i-p) structure and an inverted (p-i-n) configuration. PCE of the conventional p-i-n type PSCs is slightly higher than that of the inverted n-i-p type PSCs. However, the TiO2 electron transporting layer adopted in the conventional PSCs is formed at a high sintering temperature of >450 °C. The TiO2 electron transporting layer limits the application of conventional PSCs using flexible substrates that are not compatible with the high processing temperature. The hole extraction layer (HEL) in the inverted p-i-n type PSCs can be prepared by low-temperature solution fabrication processes, which can be adopted for achieving high performance large area flexible solar cells at a low cost. Inverted PSCs with a PCE range from 10 to 20% have been reported over the past few years. In comparison with the progresses of other photovoltaic technologies, the rapid enhancement in PCE of the PSCs offers an attractive option for commercial viability. The aim of this PhD project is to study the origin of the improvement in the performance of solution-processable inverted PSCs. The surface morphological and electronic properties of the HEL are crucial for the growth of the perovskite active layer and hence the performance of the inverted PSCs. Enhancement in short circuit current density (Jsc), reduced loss in open circuit voltage (Voc), improvement in cha Organo-metallic halide perovskite solar cells (PSCs) are considered as a promising alternative photovoltaic technology due to the advantages of low-cost solution fabrication capability and high power conversion efficiency (PCE). PSCs can be made using a conventional (n-i-p) structure and an inverted (p-i-n) configuration. PCE of the conventional p-i-n type PSCs is slightly higher than that of the inverted n-i-p type PSCs. However, the TiO2 electron transporting layer adopted in the conventional PSCs is formed at a high sintering temperature of >450 °C. The TiO2 electron transporting layer limits the application of conventional PSCs using flexible substrates that are not compatible with the high processing temperature. The hole extraction layer (HEL) in the inverted p-i-n type PSCs can be prepared by low-temperature solution fabrication processes, which can be adopted for achieving high performance large area flexible solar cells at a low cost. Inverted PSCs with a PCE range from 10 to 20% have been reported over the past few years. In comparison with the progresses of other photovoltaic technologies, the rapid enhancement in PCE of the PSCs offers an attractive option for commercial viability. The aim of this PhD project is to study the origin of the improvement in the performance of solution-processable inverted PSCs. The surface morphological and electronic properties of the HEL are crucial for the growth of the perovskite active layer and hence the performance of the inverted PSCs. Enhancement in short circuit current density (Jsc), reduced loss in open circuit voltage (Voc), improvement in charge collection efficiency (ηcc) through suppression of charge recombination were investigated systematically via controlled growth of the perovskite active layer in solution-processed inverted PSCs. Poly (3,4-ethylenedioxythiophene): poly (4-styrenesulfonate) (PEDOT:PSS) is one of the widely used solution processable conductive materials for hole transporting in different optoelectronic devices. PEDOT:PSS HEL also is a perfect electron blocking layer due to its high LUMO level. However, it has been reported that PEDOT:PSS HEL is related to the deterioration in the stability of PSCs due to its acidic and hygroscopic nature. Modification of PEDOT:PSS using solvent additives or incorporating metallic oxide nanoparticles for improving the processability and the performance of the inverted PSCs were reported. This work has been focused primary on realizing the controlled growth of perovskite active layer via HEL/perovskite interfacial modification using sodium citrate-treated PEDOT:PSS HEL and WO3-PEDOT:PSS composite HEL. Apart from investigating the properties of the modified PEDOT:PSS HELs, the purpose of the work is to improve the understanding of the effect of modified HEL on the growth of the perovskite layer, revealing the charge recombination processes under different operation conditions, analyzing change extraction probability, and thereby improving the overall performance of the PSCs. PCE of >11.30% was achieved for PSCs with a sodium citrate-modified PEDOT:PSS HEL, which is >20% higher than that of a structurally identical control device having a pristine PEDOT:PSS HEL (9.16%). The incident photon to current efficiency (IPCE) and light intensity-dependent J-V measurements reveal that the use of the sodium citrate-modified PEDOT:PSS HEL helps to boost the performance of the inverted PSCs in two ways: (1) it improves the processability of perovskite active layer on HEL, and (2) it enables to enhance the charge extraction efficiency at the HEL/perovskite interface. The suppression of charge recombination in the PSCs with a modified HEL also was examined using photocurrent-effective voltage (Jph-Veff) and transient photocurrent (TPC) measurements. Morphological and structural properties of the perovskite layers were investigated using the scanning electron microscope (SEM) and X-ray diffraction (XRD) measurements. The results reveal that high quality perovskite active layer on the modified HEL was attained forming complete perovskite phase. The surface electronic properties of the modified PEDOT:PSS and pristine PEDOT:PSS layers were studied using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) measurements. XPS results reveal that treatment of sodium citrate partially removes the PSS unit in the PEDOT:PSS, resulting in an increase in the ratio of PEDOT to PSS from 0.197 for a treated PEDOT:PSS HEL to that of 0.108 for the pristine PEDOT:PSS HEL. UPS measurements also show that there is an observable reduction in the work function of the modified HEL, implying that sodium citrate-modified PEDOT:PSS HEL possesses an improved electron blocking capability, which is beneficial for efficient operation of the inverted PSCs.;The performance enhancement in MAPbI3-based PSCs with a tungsten oxide (WO3)-PEDOT:PSS composite HEL also was analyzed. The uniform composite WO3-PEDOT:PSS HEL was formed on indium tin oxide (ITO) surface by solution fabrication process. The morphological and surface electronic properties of WO3-PEDOT:PSS composite film were examined using AFM, XPS, UPS and Raman Spectroscopy. SEM images reveal that the perovskite films grown on the composite HEL had a full coverage without observable pin holes. XRD results show clearly that no residual of lead iodide phase was observed, suggesting a complete perovskite phase was obtained for the perovskite active layer grown on the composite HEL. The volume ratio of WO3 to PEDOT:PSS of 1:0.25 was optimized for achieving enhanced current density and Voc in the PSCs. It is demonstrated clearly that the use of the WO3-PEDOT:PSS composite HEL helps to improve the charge collection probability through suppression of the charge recombination at the MAPbI3/composite HEL interface. The charge extraction efficiency at the perovskite/PEDOT:PSS and perovskite/composite HEL interfaces were investigated by analyzing the PL quenching efficiency of the MAPbI3 active layer. It is shown that the PL efficiency quenching at the MAPbI3/composite HEL samples is one order of magnitude higher than that measured for the perovskite/pristine PEDOT:PSS sample, suggesting an enhanced hole extraction probability at the MAPbI3/composite HEL interface. The combined effects of improved perovskite crystal growth and enhanced charge extraction capabilities result in the inverted PSCs with a PCE of 12.65%, which is 22% higher than that of a structurally identical control device (10.39%). The use of the WO3-PEDOT:PSS composite HEL also benefits the efficient operation of the PSCs, demonstrated in the stability test, as compared to that of the control cell under the same aging conditions. With the progresses made in improving the performance of MAPbI3-based PSCs, the research was extended to study the performance of efficient PSCs with mixed halide of MA0.7FA0.3Pb (I0.9Br0.1)3. The effect of the annealing temperature on the growth of the mixed MA0.7FA0.3Pb (I0.9Br0.1)3 perovskite active layer was analyzed. It was found that the optimal growth of the mixed perovskite active layer occurred at an annealing temperature of 100°C. UPS results reveal that the ionization potential of 5.76 eV measured for the mixed cation perovskite is lower than that of MAPbI3-based single cation perovskite layer (5.85 eV), while the corresponding electron affinity of the mixed perovskite was 4.28 eV and that for the MAPbI3 layer was 4.18 eV, respectively. The changes in the bandgap and the energy levels of the MA0.7FA0.3Pb (I0.9Br0.1)3 and MAPbI3 active layers were examined using UV-vis absorption spectroscopy and UPS measurements. Compared to the MAPbI3-based control cell, a 23% increase in Jsc, a 15% increase in Voc and an overall 25% increase in PCE for the MA0.7FA0.3Pb (I0.9Br0.1)3 were achieved as compared to that of the MAPbI3-based PSCs. An obvious improvement in charge collection efficiency in MA0.7FA0.3Pb (I0.9Br0.1)3-based PSCs operated at different Veff was clearly manifested by the light intensity dependent J-V characteristic measurements. PL quenching efficiency also shows the charge transfer between MA0.7FA0.3Pb (I0.9Br0.1)3 and PEDOT:PSS HEL is one order of magnitude higher as compare to that in the MAPbI3-based PSCs, suggesting the formation of improved interfacial properties at the MA0.7FA0.3Pb (I0.9Br0.1)3/HEL interface. The impact of incorporating mixed MA0.7FA0.3Pb (I0.9Br0.1)3 perovskite active layer on PCE and the stability of the PSCs was further studied using a combination of TPC measurement and aging test. The stability of MA0.7FA0.3Pb (I0.9Br0.1)3- and MAPbI3-based PSCs with respect to the aging time was monitored for a period of >2 months. The MA0.7FA0.3Pb (I0.9Br0.1)3-based PSCs are more stable compared to the MAPbI3-based PSCs aged under the same conditions. The aging test supports the findings made with the TPC and light intensity dependent J-V measurements. It shows that the improved interfacial quality at the perovskite/HEL and the enhanced charge extraction capability are favorable for efficient and stable operation of MA0.7FA0.3Pb (I0.9Br0.1)3-based PSCs.

Much public and private effort is being directed towards the development of more sustainable chemical feedstocks, yet the associated complexities of technological transitions and the technical, institutional and policy-related challenges they raise are often not wholly recognised. This thesis aims to develop an understanding of the key dynamics of technological change in the chemical industry, with respect to changes in feedstocks and the influence of the changing energy (and climate policy) landscape. It builds on, and contributes to, the ‘innovations’ literature that seeks to translate empirical research on past technological transitions into practical guidance for policy-makers. In particular, this thesis explores the relevance of the close relationship – or ‘co-evolution’ – between chemicals and liquid fuels production, which has not been analysed elsewhere. Transitions between technological systems involve evolutionary processes. The past both shapes the current system and influences future options and pathways. This thesis investigates the historical transition from coal-based to petrochemical feedstocks in the UK (1921-1967), applying a system dynamics approach to extract and elucidate the key interrelationships between technologies, policy and society. The findings are then used to inform a series of interviews with key organisations to gain insights into expectations for renewable raw materials (RRM) in the UK. The results provide a strong indication of the decision-making procedures of actors, and tensions between different industrial activities. They thus provide an empirical basis for developing foresight scenarios that might help inform the current debate about technological transitions, especially those to RRM. This thesis shows that the technological trajectory of the organic chemical industry has for many decades been influenced heavily by governmental attempts to steer technological change towards a changing set of policy priorities. This process has been accompanied by attempts of industrialists to steer policy priorities towards preferred technological trajectories. Parallels can be drawn with the current attempts of policymakers to achieve greater societal sustainability. Results indicate that the innovation system around RRM is already experiencing the socio-technical dynamics of regime disruption and competing designs.

Na presente tese foram preparados poliésteres derivados de dois materiais renováveis o ácido 2,5-furanodicarboxílico (AFD) e a isoidida. Foram também preparados monômeros dihidroxílados para uso em poliesterificações e em reações com diisocianatos contendo um aduto de Diels-Alder (DA) formado pela reação de um grupo furano e uma maleimida (reação entre uma bismaleimida e o álcool furfurílico). Esses diois foram utilizados na preparação de poliésteres e poliuretanos termorreversíveis. A termorreversibilidade dos materiais preparados advém do fato de que os adutos de DA são termorreversíveis (rDA). Portanto, ao aquecer os poliésteres preparados com aduto-DA são originados monômeros difuncionais com grupos furano e/ou maleimida. O produto da rDA pode então ser repolimerizado, mas não via reações de poliesterificação ou isocianato/hidroxila, mas pelo acoplamento furano/maleimida (DA). Por fim uma nova rota para a obtenção de copolímeros aleatórios foi investigada. Essa rota consiste em provocar a rDA de uma mistura de dois homopolímeros distintos obtidos por polimerização em etapas contendo no interior de suas unidades repetitivas adutos de Diels-Alder e em seguida provocar a sua repolimerização via DA para dar origem a um copolímero aleatório. Os materiais foram caracterizados por suas estruturas químicas por Espectroscopia na região do infravermelho com transformada de Fourier (FTIR), ressonância magnética nuclear de próton (RMN ¹H). Foram feitos ensaios de cromatografia de permeação de gel (GPC), onde notou-se uma massa média numérica e ponderal para os poliésteres obtidos a partir do AFD e também para o poliéster e poliuretano termorreversíveis de aproximadamente 1600 g.mol¹. Nos ensaios de calorimetria exploratória diferencial (DSC) foi obtido Tgs variados para os poliésteres obtidos a partir do AFD indo de 88 a 159ºC, de 80ºC para o poliuretano termorreversível e de 106ºC para o poliéster termorreversível. Para a análise termogravimétrica (TGA) foi observado temperaturas de degradação para os poliésteres obtidos a partir do AFD em torno de 280ºC. Para a análise térmica dinâmico-mecânicas (DMTA) obteve-se Tg\'s em 117, 123 e 120ºC para o poliéster, o poliuretano e o copolímero termorreversíveis.
In this thesis it was prepared polyesters of two renewable monomers, the 2.5-furandicarboxylic acid and isoidide. Dihydroxy monomers were also prepared for use in polysterification and in reactions with diisocyanates, both containing Diels-Alder adduct in the molecule formed by the reaction of a furan group and a maleimide (reaction between bismaleimide and furfuryl alcohol). These diols were used in the preparation of thermoreversible polyesters and polyurethanes. The thermoreversibility of these materials comes from the fact that the DA adducts are thermoreversible (rDA). Therefore, heating these polymers give rise to difunctional monomers with an adduct-DA with furan and/or maleimide functions. The product of the rDA may then be polymerized not via polysterification reactions or isocyanate/hydroxyl, but by furan/maleimide coupling (DA) restoring the DA adduct. Finaly a new route to obtain random copolymers was investigated. This route consists in the rDA of a mixture of two different homopolymers obtained by polymerization in stages containing adducts producing monomers with furan and maleimide functions that can be polymerization via DA reaction to give a random copolymer. The materials were characterized by their chemical structures by infrared spectroscopy (FTIR), nuclear magnetic resonance of proton (¹H-NMR), gel permeation chromatography (GPC), experiments were made, where it was noticed a number and weight average mass for the polyesters obtained from the AFD and also for the thermoreversible polyester and polyurethane 1600 gmol¹. In differential scanning calorimetry tests (DSC) was obtained Tg\'s for various polyesters obtained from the AFD ranging from 88 to 159°C, 80°C for the thermoreversible polyurethane and 106°C for the thermoreversible polyester. For the thermogravimetric analysis (TGA) was observed degradation temperatures for the polyesters obtained from the AFD around 280°C. For dynamic mechanical thermal analysis (DMTA) Tg was obtained in 117, 123 and 120°C for polyester, polyurethane and copolymer thermoreversible.

O presente trabalho teve como motivação investigar a viabilidade na utilização de polióis, produzidos a partir da oxidação induzida de óleo de soja comercial e utilizar estes como precursores na síntese de revestimentos híbridos de poliuretano-ureia. O óleo de soja foi escolhido por ter baixo custo, ser oriundo de fontes renováveis e apresentar em sua molécula locais com potencialidade para modificação química. Os polióis produzidos por oxidação induzida foram caracterizados por titulometria, espectroscopia na região do infravermelho com transformada de Fourier (FTIR), espectroscopia de ressonância magnética nuclear do próton 1H (RMN 1H), cromatografia por permeação em gel (GPC) para identificar a formação de grupos hidroxila em sua molécula e determinar o tempo adequado de oxidação do óleo. Após serem caracterizados, os polióis foram utilizados na síntese de revestimentos híbridos de poliuretano-ureia para serem utilizados na proteção de superfícies metálicas. Os precursores utilizados na síntese foram o óleo de soja oxidado durante 24 h (OSO-24h), óleo de soja oxidado durante 48 h (OSO-48h), 4,4'-difenil metano diisocianato (MDI), 3-aminopropil trimetoxisilano (APTMS). As análises de FTIR dos revestimentos híbridos revelaram a presença de grupos Si-O-Si, indicando a formação de uma rede híbrida, a qual também foi identificada pela análise de espectroscopia de ressonância magnética nuclear do próton 29Si (RMN 29Si), quando foi verificada a presença de estruturas T0, T1, T2 e T3 (onde o índice 0, 1, 2 ou 3 indica o número de grupos de siloxanos ligados ao átomo de silício). O mapa composicional obtido por espectroscopia de energia dispersiva (EDS) revelou que as amostras contendo aminosilano apresentam estruturas com separação de fase; isto aconteceu devido à diferença na taxa relativa de formação dos grupos ureias frente aos grupos uretanos. As análises de difração de raios X (DRX) exibem um perfil típico de materiais amorfos e a técnica de espalhamento de raios X a baixo ângulo (SAXS) revela que os domínios rígidos possuem formatos esféricos com tamanhos entre 1-6 nm. Os revestimentos aplicados em substratos metálicos foram aprovados nos testes de adesão, resistência ao impacto e flexibilidade segundo as normas da sociedade americana de testes e materiais (ASTM), entretanto, o ensaio de névoa salina revelou que os revestimentos sem o aminosilano apresentam maior resistência à corrosão, em comparado com os materiais híbridos, em virtude da formação de uma fase rica em silício, a qual atua como inicializadora da reação de corrosão.
Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-10-17T15:37:27Z No. of bitstreams: 1 Tese Pedro Antonio Ourique.pdf: 4145729 bytes, checksum: 0326f707659828778e2d95c67c9e81c9 (MD5)
Made available in DSpace on 2016-10-17T15:37:27Z (GMT). No. of bitstreams: 1 Tese Pedro Antonio Ourique.pdf: 4145729 bytes, checksum: 0326f707659828778e2d95c67c9e81c9 (MD5) Previous issue date: 2016-10-17
Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS.
Motivation of the work was to investigate the synthesis of polyols obtained from air induced oxidation of the commercial soybean oil and use these as precursors in the preparation of polyurethane-urea hybrid coatings. Soybean oil is a feedstock that has low cost, and it comes from renewable sources. This molecule has the potential for chemical modification and use in different applications. The synthesized polyols were characterized by titration, FTIR, 1H NMR and GPC for evaluation formation of hydroxyl groups in oxidized soybean oil. After characterization polyols, were used in the synthesis of polyurethane-urea hybrid coatings for use in metal surfaces protection. The monomers used in the synthesis of hybrid coatings were oxidized soybean oil for 24 h (OSO-24), oxidized soybean oil for 48 h (OSO-48h), 4,4'-diphenyl methane diisocyanate (MDI), 3-aminopropyl trimethoxysilane (APTMS). FTIR analysis of the hybrid coatings revealed the presence of Si-O-Si bands, indicating the formation of a hybrid network, which was also identified by 29Si NMR, showing the formation of structures T0, T1, T2 and T3. SEM analysis and compositional map generated by EDS indicate that the samples with APTMS presented phase separated structures; this occurred during the difference in the relative rate of formation of urea groups when compared to urethane groups. On the other hand, the synthesized materials were amorphous and had rigid spherical shape domains with sizes between 16 nm. The films produced, when used as coatings, exhibited satisfactory mechanical behavior and excellent adhesion to metal substrates. However, its corrosion resistance is limited during of the formation of silicon rich phases.

This research was established due to an increase of interest in renewable energy sources and utilisation of various wastes and biomass. Gasification is currently one of the most promising thermal-chemical conversion techniques for recovering energy from waste, and the pyrolytic behaviour of secondary refuse fuel (SRF) briquettes and biomass-derived fuels is the starting point for the process. The purpose of this study was to evaluate the pyrolytic characteristics of SRF briquettes and biomass materials, suggest a kinetic model for simulating the pyrolytic process and obtaining the kinetic parameters, and then predict the yield of volatile products in pyrolysis. Knowledge of the chemical composition, the thermal behaviour and the reactivity of SRF briquettes and their blends with other materials, such as biomass and plastic during pyrolysis is very important for the effective design operation of gasification units. The kinetics of the pyrolysis of simulated SRF briquettes, SRF briquettes and pulverised biomass samples was successfully modelled by a scheme consisting of two independent general order parallel reactions of the main components which were hemicellulose, cellulose, lignin and plastic. The kinetic parameters estimated through the model were comparable with those reported in the literature. In this research, activation energy values varied between 30 – 70 kJ/mol for lignin pyrolysis, 96 – 137 kJ/mol for hemicellulose and cellulose pyrolysis, and about 260 kJ/mol for plastic pyrolysis. Biomass has a very high volatile content. Adding biomass into SRF briquettes could increase the volatile yield. Increasing the plastic content of SRF briquettes could increase the volatile yield, the derivative thermogravimetric (DTG) peak height and the repeatability of pyrolysis. Inorganic component could shift the cellulose pyrolysis to a lower temperature and cause the hemicellulose pyrolysis and the cellulose pyrolysis highly overlapped, but it could have a positive effect by acting as catalysts and lower the activation energy in the pyrolysis of hemicellulose and cellulose. Molasses used as a binder could improve the DTG peak height and restrain the curve shifting effect of inorganic component on the hemicellulose and cellulose pyrolysis, but couldn’t restrain the lignin pyrolysis at low temperatures during the hemicellulose and cellulose pyrolysis. Molasses could restrain the effect of the lignin pyrolysis at high temperatures on the plastic pyrolysis. Mechanical biological treatment (MBT) process could highly improve the volatile yield and improve the DTG peak height of SRF briquettes.

The need to find biodegradable alternatives for common polymer materials has risen due to the increase in pollution (soil and water) and the effects that it has on the ocean and wildlife. Alternatives can be found by turning to plant-based oils, for example castor oil, to be used in the synthesis of a variety of monomers. Castor oil is suitable as it is non-edible; thus its use does not deplete food sources and it has high chemical reactivity. In this study, medical grade castor oil was maleated by the addition of maleic anhydride to form maleated castor oil (MACO). This reaction was performed at 98 ˚C for five hours. The completion of the reaction was monitored using acid value. The maleated castor oil was reacted with styrene monomer (at 60 ˚C) and thermally cured to form a tough but flexible polymer (MACOPS). Curing took place for two hours at 90 ˚C, two hours at 120 ˚C and 1 hour at 160 ˚C. Additionally, the synthesized polymer matrix was reinforced with alkalized greige fibres (consisting of a hemp and cotton mix) using a hand lay-up process. Mechanical tests - tensile, flexural and impact strength - were performed on the neat and reinforced polymer. Comparison tests (to determine mechanical properties) were also conducted on commercial general purpose polystyrene (GPPS) and high impact polystyrene (HIPS). Scanning electron microscopy (SEM) was performed on the tensile fracture surfaces of the reinforced matrix. The crosslink density, contact angles and density of the synthesized polymer were determined. Differential scanning calorimetry (DSC) was used to determine the glass transition temperature(s) of the synthesized and commercial polymers. Thermogravimetry was performed on the synthesized matrix as well as the commercial polymers to determine operating temperatures. Raman spectroscopy was used to obtain structural information on the synthesized polymer as well as confirm the successful completion of the maleation reaction. To test for the compostability of the maleated castor oil-polystyrene polymer matrix, biodegradability tests were conducted for a period of ten weeks. The degraded samples underwent tensile testing and the contact angles were determined. Transmission electron microscopy (TEM) was used to see the distribution of polystyrene throughout HIPS and the MACOPS matrix. The acid value at the start of the reaction was 80.1/100 mgNaOH and at the end of the reaction the acid value decreased to 74.7/100 mgNaOH. A decrease in acid value indicated that the maleic anhydride stopped reacting at the end of the reaction. An increase in viscosity of the mixture served as an indication that the maleation reaction did take place. ASTM D6110 was used for the Charpy impact test. HIPS performed as expected with the highest impact strength of 58.4 kJ/m2 . The addition of MACO to styrene monomer led to an increase in the toughness of the end product. An increase was observed for both the MACOPS and reinforced MACOPS compared to GPPS. MACOPS and reinforced MACOPS had impact strengths of 41.5 kJ/m2 and 45.0 kJ/m2 respectively. The addition of the reinforcing greige fibres did not significantly improve the impact strength. GPPS had the lowest impact strength of 33.9 kJ/m2 . Tensile tests were conducted according to ASTM D638. For MACOPS an ultimate tensile strength (UTS) of 23.0 MPa and a Young's modulus of 983 MPa were found. GPPS on the other hand had a much higher UTS and Young's modulus of 44.8 MPa and 3.3 GPa respectively. Once again the MACOPS had tensile properties closer to those of HIPS. The UTS and Young's modulus of HIPS was 13.5 MPa and 1.5 GPa respectively. The reinforced MACOPS did not perform very well under tension with a UTS of 13.1 MPa and a Young's modulus of only 283 MPa. The theoretical modulus of the composite was calculated using the Rule of Mixtures and the Halpin-Tsai model to determine the efficiency of the greige fibres as reinforcement. The efficiency was determined to be less than 30%. Flexural tests were conducted according to ASTM D7264. A significant difference in the flexibility of the synthesized polymer was found when compared to GPPS. MACOPS had a maximum flexural strength of 22.1 MPa whereas GPPS had a flexural strength of 74.4 MPa. The MACOPS had flexural properties closer to that of HIPS which had a flexural strength of 27.2 MPa. The reinforced MACOPS had a flexural strength of 12.2 MPa. This was ascribed to the presence of significant delamination. GPPS and HIPS have no crosslinks between the polymer chains. A crosslink density of 2.1 x 10-3 mol/cm3 was determined for the MACOPS matrix. This could point to co-polymer formation between MACO and polystyrene. Raman spectroscopy was used to determine if the maleation of castor oil took place successfully. Maleic anhydride has signature absorption bands at 1850 cm-1 and 1790 cm-1 . These peaks were absent in the MACO spectrum, which suggests complete reaction. Signature peaks of both the MACO and GPPS were present in the spectrum of MACOPS. This also may point to co-polymer formation. A Raman map of MACOPS showed uniform distribution of polystyrene throughout the sample whereas HIPS had numerous gaps where polystyrene was of low intensity. This points to the presence of sections containing polybutadiene. Therefore MACOPS can be characterized as either a co-polymer or an interpenetrating polymer network. MACOPS displayed two glass transition temperatures (Tg) when analyzed with DSC. A small (low intensity) glass transition temperature peak was observed at 93.2 °C and a second of higher intensity at 54.9 ˚C. Two glass transition temperature can point to an interpenetrating polymer network. The Tg of 54.9 ˚C was assigned to a co-polymer. The Tg of 93.2 ˚C is possibly due to a small amount of homo-polymerized polystyrene. Due to the fact that the glass transition temperature is relatively close to ambient temperature, the matrix is relatively flexible but not elastomeric; hard and tough but not very brittle. Thermogravimetry indicated a thermal degradation onset temperature of 336 °C for the MACOPS matrix. The onset temperature for thermal degradation of MACOPS is lower than those of HIPS and GPPS. After biodegradability testing, no significant loss in mechanical properties was observed for the MACOPS matrix and reinforced composite. MACOPS showed the most mass loss (10.4%) in comparison with the other materials. A significant decrease was seen in the contact angle measurements of the degraded reinforced MACOPS. The contact angle decreased from 88˚ (original) to 54.2˚ (degraded). This points to surface changes as a result of degradation that decreases the hydrophobicity of the material. It can be seen that the addition of MACO to styrene monomer most likely results in an IPN with a degree of crosslinking. The properties of this matrix is closer to those of HIPS than GPPS. The matrix is hard, tough and more flexible than GPPS. At room temperature the MACOPS matrix is used just above its glass transition temperature. Reinforcing the matrix with greige fibres led to a decrease in mechanical properties. Thus the fibres acted only as a filler. The synthesized MACOPS matrix is hydrophilic and shows no significant degradation when placed in compost after a period of 10 weeks.

Phase change material (PCM)-based ocean thermal energy harvesting is a relatively new method, which extracts the thermal energy from the temperature gradient in the ocean thermocline. Its basic idea is to utilize the temperature variation along the ocean water depth to cyclically freeze and melt a specific kind of PCM. The volume expansion, which happens in the melting process, is used to do useful work (e.g., drive a turbine generator), thereby converting a fraction of the absorbed thermal energy into mechanical energy or electrical energy. Compared to other ocean energy technologies (e.g., wave energy converters, tidal current turbines, and ocean thermal energy conversion), the proposed PCM-based approach can be easily implemented at a small scale with a relatively simple structural system, which makes it a promising method to extend the range and service life of battery-powered devices, e.g, autonomous underwater vehicles (AUVs). This dissertation presents a combined theoretical and experimental study of the PCM-based ocean thermal energy harvesting approach, which aims at demonstrating the feasibility of the proposed approach and investigating possible methods to improve the overall performance of prototypical systems. First, a solid/liquid phase change thermodynamic model is developed, based on which a specific upperbound of the thermal efficiency is derived for the PCM-based approach. Next, a prototypical PCM-based ocean thermal energy harvesting system is designed, fabricated, and tested. To predict the performance of specific systems, a thermo-mechanical model, which couples the thermodynamic behaviors of the fluid materials and the elastic behavior of the structural system, is developed and validated based on the comparison with the experimental measurement. For the purpose of design optimization, the validated thermo-mechanical model is employed to conduct a parametric study. Based on the results of the parametric study, a new scalable and portable PCM-based ocean thermal energy harvesting system is developed and tested. In addition, the thermo-mechanical model is modified to account for the design changes. However, a combined analysis of the results from both the prototypical system and the model reveals that achieving a good performance requires maintaining a high internal pressure, which will complicate the structural design. To mitigate this issue, the idea of using a hydraulic accumulator to regulate the internal pressure is proposed, and experimentally and theoretically examined. Finally, a spatial-varying Robin transmission condition for fluid-structure coupled problems with strong added-mass effect is proposed and investigated using fluid structure interaction (FSI) model problems. This can be a potential method for the future research on the fluid-structure coupled numerical analysis of AUVs, which are integrated with and powered by the PCM-based thermal energy harvesting devices.
Doctor of Philosophy